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            <h2 class="toc-title">目录</h2>
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        </div><article class="page single"><h1 class="single-title animated flipInX">Spring源码 - AOP 代理实例的创建</h1><div class="post-meta">
            <div class="post-meta-line"><span class="post-author"><a href="https://wlizhi.cc" title="Author" target="_blank" rel="noopener noreffer author" class="author"><i class="fas fa-user-circle fa-fw"></i>Wlizhi</a></span>&nbsp;<span class="post-category">收录于 <a href="/categories/spring/"><i class="far fa-folder fa-fw"></i>spring</a></span></div>
            <div class="post-meta-line"><i class="far fa-calendar-alt fa-fw"></i>&nbsp;<time datetime="2020-12-01">2020-12-01</time>&nbsp;<i class="fas fa-pencil-alt fa-fw"></i>&nbsp;约 2805 字&nbsp;
                <i class="far fa-clock fa-fw"></i>&nbsp;预计阅读 6 分钟&nbsp;<span id="/posts/spring/11-aop-proxy-create-processor/" class="leancloud_visitors" data-flag-title="Spring源码 - AOP 代理实例的创建">
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  <ul>
    <li><a href="#1-创建实例的流程">1 创建实例的流程</a></li>
    <li><a href="#2-构建advisor---buildadvisors">2 构建Advisor - buildAdvisors</a></li>
    <li><a href="#3-生成代理实例---getproxy">3 生成代理实例 - getProxy</a></li>
  </ul>
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            </div><div class="content" id="content"><p>spring源码系列文章，示例代码的中文注释，均是 copy 自 <a href="https://gitee.com/wlizhi/spring-framework" target="_blank" rel="noopener noreffer">https://gitee.com/wlizhi/spring-framework</a> 。</p>
<p>链接中源码是作者从 github 下载，并以自身理解对核心流程及主要节点做了详细的中文注释。</p>
<hr>
<h2 id="1-创建实例的流程">1 创建实例的流程</h2>
<p>创建代理实例在 createProxy() 中进行。</p>
<p>createProxy() 中有两个比较关键的方法：</p>
<ol>
<li>buildAdvisors()</li>
<li>getProxy()</li>
</ol>
<p>源码如下：</p>
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<pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span> <span class="kd">abstract</span> <span class="kd">class</span> <span class="nc">AbstractAutoProxyCreator</span> <span class="kd">extends</span> <span class="n">ProxyProcessorSupport</span>
</span></span><span class="line"><span class="cl">		<span class="kd">implements</span> <span class="n">SmartInstantiationAwareBeanPostProcessor</span><span class="o">,</span> <span class="n">BeanFactoryAware</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">    <span class="kd">protected</span> <span class="n">Object</span> <span class="nf">createProxy</span><span class="o">(</span><span class="n">Class</span><span class="o">&lt;?&gt;</span> <span class="n">beanClass</span><span class="o">,</span> <span class="nd">@Nullable</span> <span class="n">String</span> <span class="n">beanName</span><span class="o">,</span>
</span></span><span class="line"><span class="cl">			<span class="nd">@Nullable</span> <span class="n">Object</span><span class="o">[]</span> <span class="n">specificInterceptors</span><span class="o">,</span> <span class="n">TargetSource</span> <span class="n">targetSource</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">        <span class="c1">// 省略...
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>		<span class="c1">// 注意这个ProxyFactory，里面封装了 Advisors
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>		<span class="n">ProxyFactory</span> <span class="n">proxyFactory</span> <span class="o">=</span> <span class="k">new</span> <span class="n">ProxyFactory</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">		<span class="n">proxyFactory</span><span class="o">.</span><span class="na">copyFrom</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">		<span class="c1">// 省略...
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>		<span class="c1">// TODO 重点：构建增强对象，这里会在原有的Advisor列表中，增加存在的MethodInterceptor
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>		<span class="n">Advisor</span><span class="o">[]</span> <span class="n">advisors</span> <span class="o">=</span> <span class="n">buildAdvisors</span><span class="o">(</span><span class="n">beanName</span><span class="o">,</span> <span class="n">specificInterceptors</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">		<span class="n">proxyFactory</span><span class="o">.</span><span class="na">addAdvisors</span><span class="o">(</span><span class="n">advisors</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">		<span class="n">proxyFactory</span><span class="o">.</span><span class="na">setTargetSource</span><span class="o">(</span><span class="n">targetSource</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">		<span class="n">customizeProxyFactory</span><span class="o">(</span><span class="n">proxyFactory</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">		<span class="n">proxyFactory</span><span class="o">.</span><span class="na">setFrozen</span><span class="o">(</span><span class="k">this</span><span class="o">.</span><span class="na">freezeProxy</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">		<span class="k">if</span> <span class="o">(</span><span class="n">advisorsPreFiltered</span><span class="o">())</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">			<span class="n">proxyFactory</span><span class="o">.</span><span class="na">setPreFiltered</span><span class="o">(</span><span class="kc">true</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">		<span class="o">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">		<span class="c1">// TODO 重点：生成代理对象
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>		<span class="k">return</span> <span class="n">proxyFactory</span><span class="o">.</span><span class="na">getProxy</span><span class="o">(</span><span class="n">getProxyClassLoader</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">	<span class="o">}</span>
</span></span><span class="line"><span class="cl"><span class="o">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><h2 id="2-构建advisor---buildadvisors">2 构建Advisor - buildAdvisors</h2>
<p>来到 buildAdvisors() 源码：</p>
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<pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span> <span class="kd">abstract</span> <span class="kd">class</span> <span class="nc">AbstractAutoProxyCreator</span> <span class="kd">extends</span> <span class="n">ProxyProcessorSupport</span>
</span></span><span class="line"><span class="cl">		<span class="kd">implements</span> <span class="n">SmartInstantiationAwareBeanPostProcessor</span><span class="o">,</span> <span class="n">BeanFactoryAware</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">    <span class="kd">protected</span> <span class="n">Advisor</span><span class="o">[]</span> <span class="nf">buildAdvisors</span><span class="o">(</span><span class="nd">@Nullable</span> <span class="n">String</span> <span class="n">beanName</span><span class="o">,</span> <span class="nd">@Nullable</span> <span class="n">Object</span><span class="o">[]</span> <span class="n">specificInterceptors</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">		<span class="c1">// Handle prototypes correctly...
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>		<span class="c1">// 获取已有的方法拦截器，名称，并包装成Advisor
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>		<span class="n">Advisor</span><span class="o">[]</span> <span class="n">commonInterceptors</span> <span class="o">=</span> <span class="n">resolveInterceptorNames</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">		<span class="n">List</span><span class="o">&lt;</span><span class="n">Object</span><span class="o">&gt;</span> <span class="n">allInterceptors</span> <span class="o">=</span> <span class="k">new</span> <span class="n">ArrayList</span><span class="o">&lt;&gt;();</span>
</span></span><span class="line"><span class="cl">		<span class="k">if</span> <span class="o">(</span><span class="n">specificInterceptors</span> <span class="o">!=</span> <span class="kc">null</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">			<span class="n">allInterceptors</span><span class="o">.</span><span class="na">addAll</span><span class="o">(</span><span class="n">Arrays</span><span class="o">.</span><span class="na">asList</span><span class="o">(</span><span class="n">specificInterceptors</span><span class="o">));</span>
</span></span><span class="line"><span class="cl">			<span class="k">if</span> <span class="o">(</span><span class="n">commonInterceptors</span><span class="o">.</span><span class="na">length</span> <span class="o">&gt;</span> <span class="n">0</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">				<span class="k">if</span> <span class="o">(</span><span class="k">this</span><span class="o">.</span><span class="na">applyCommonInterceptorsFirst</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">					<span class="n">allInterceptors</span><span class="o">.</span><span class="na">addAll</span><span class="o">(</span><span class="n">0</span><span class="o">,</span> <span class="n">Arrays</span><span class="o">.</span><span class="na">asList</span><span class="o">(</span><span class="n">commonInterceptors</span><span class="o">));</span>
</span></span><span class="line"><span class="cl">				<span class="o">}</span>
</span></span><span class="line"><span class="cl">				<span class="k">else</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">					<span class="n">allInterceptors</span><span class="o">.</span><span class="na">addAll</span><span class="o">(</span><span class="n">Arrays</span><span class="o">.</span><span class="na">asList</span><span class="o">(</span><span class="n">commonInterceptors</span><span class="o">));</span>
</span></span><span class="line"><span class="cl">				<span class="o">}</span>
</span></span><span class="line"><span class="cl">			<span class="o">}</span>
</span></span><span class="line"><span class="cl">		<span class="o">}</span>
</span></span><span class="line"><span class="cl">        <span class="c1">// 省略部分代码...
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>		<span class="n">Advisor</span><span class="o">[]</span> <span class="n">advisors</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Advisor</span><span class="o">[</span><span class="n">allInterceptors</span><span class="o">.</span><span class="na">size</span><span class="o">()];</span>
</span></span><span class="line"><span class="cl">		<span class="k">for</span> <span class="o">(</span><span class="kt">int</span> <span class="n">i</span> <span class="o">=</span> <span class="n">0</span><span class="o">;</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="n">allInterceptors</span><span class="o">.</span><span class="na">size</span><span class="o">();</span> <span class="n">i</span><span class="o">++)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">			<span class="c1">// 在这里进行构建的，最终，所有的通知方法都会封装成Advisor。
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>			<span class="c1">// 实际上我们自己定义的切面，到这里时，都已经是Advisor了，没有做任何处理直接返回了。
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>			<span class="c1">// 之所以在这里要再进行封装，是因为Spring中涉及过多的拦截器，增强器，增强方法等方式来对逻辑进行增强，
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>			<span class="c1">// 有些情况allInterceptors中可能存在Advice对象，所以非常有必要统一封装成Advisor
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>			<span class="n">advisors</span><span class="o">[</span><span class="n">i</span><span class="o">]</span> <span class="o">=</span> <span class="k">this</span><span class="o">.</span><span class="na">advisorAdapterRegistry</span><span class="o">.</span><span class="na">wrap</span><span class="o">(</span><span class="n">allInterceptors</span><span class="o">.</span><span class="na">get</span><span class="o">(</span><span class="n">i</span><span class="o">));</span>
</span></span><span class="line"><span class="cl">		<span class="o">}</span>
</span></span><span class="line"><span class="cl">		<span class="k">return</span> <span class="n">advisors</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">	<span class="o">}</span>
</span></span><span class="line"><span class="cl"><span class="o">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>从源码中可以看出，首选获取了一个 Advisor 数组，然后与之前搜集好的 Advisor 数组进行合并。</p>
<p>对合并后的结果进行遍历，然后调用 advisorAdapterRegistry.wrap()，wrap() 方法的作用，源码注释中有详细说明。</p>
<p>简单看一下 resolveInterceptorNames() 的过程：</p>
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<pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span> <span class="kd">abstract</span> <span class="kd">class</span> <span class="nc">AbstractAutoProxyCreator</span> <span class="kd">extends</span> <span class="n">ProxyProcessorSupport</span>
</span></span><span class="line"><span class="cl">		<span class="kd">implements</span> <span class="n">SmartInstantiationAwareBeanPostProcessor</span><span class="o">,</span> <span class="n">BeanFactoryAware</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">    <span class="kd">private</span> <span class="n">Advisor</span><span class="o">[]</span> <span class="nf">resolveInterceptorNames</span><span class="o">()</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">		<span class="n">BeanFactory</span> <span class="n">bf</span> <span class="o">=</span> <span class="k">this</span><span class="o">.</span><span class="na">beanFactory</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">		<span class="n">ConfigurableBeanFactory</span> <span class="n">cbf</span> <span class="o">=</span> <span class="o">(</span><span class="n">bf</span> <span class="k">instanceof</span> <span class="n">ConfigurableBeanFactory</span> <span class="o">?</span> <span class="o">(</span><span class="n">ConfigurableBeanFactory</span><span class="o">)</span> <span class="n">bf</span> <span class="o">:</span> <span class="kc">null</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">		<span class="n">List</span><span class="o">&lt;</span><span class="n">Advisor</span><span class="o">&gt;</span> <span class="n">advisors</span> <span class="o">=</span> <span class="k">new</span> <span class="n">ArrayList</span><span class="o">&lt;&gt;();</span>
</span></span><span class="line"><span class="cl">		<span class="c1">// 这里会根据interceptorNames中存储的拦截器名称，获取到对应的bean实例，最终包装成Advisor，添加到列表中返回。
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>		<span class="k">for</span> <span class="o">(</span><span class="n">String</span> <span class="n">beanName</span> <span class="o">:</span> <span class="k">this</span><span class="o">.</span><span class="na">interceptorNames</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">			<span class="k">if</span> <span class="o">(</span><span class="n">cbf</span> <span class="o">==</span> <span class="kc">null</span> <span class="o">||</span> <span class="o">!</span><span class="n">cbf</span><span class="o">.</span><span class="na">isCurrentlyInCreation</span><span class="o">(</span><span class="n">beanName</span><span class="o">))</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">				<span class="n">Assert</span><span class="o">.</span><span class="na">state</span><span class="o">(</span><span class="n">bf</span> <span class="o">!=</span> <span class="kc">null</span><span class="o">,</span> <span class="s">&#34;BeanFactory required for resolving interceptor names&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">				<span class="n">Object</span> <span class="n">next</span> <span class="o">=</span> <span class="n">bf</span><span class="o">.</span><span class="na">getBean</span><span class="o">(</span><span class="n">beanName</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">				<span class="n">advisors</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="k">this</span><span class="o">.</span><span class="na">advisorAdapterRegistry</span><span class="o">.</span><span class="na">wrap</span><span class="o">(</span><span class="n">next</span><span class="o">));</span>
</span></span><span class="line"><span class="cl">			<span class="o">}</span>
</span></span><span class="line"><span class="cl">		<span class="o">}</span>
</span></span><span class="line"><span class="cl">		<span class="k">return</span> <span class="n">advisors</span><span class="o">.</span><span class="na">toArray</span><span class="o">(</span><span class="k">new</span> <span class="n">Advisor</span><span class="o">[</span><span class="n">0</span><span class="o">]);</span>
</span></span><span class="line"><span class="cl">	<span class="o">}</span>
</span></span><span class="line"><span class="cl"><span class="o">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>代码流程是：首先对 interceptorNames 进行遍历，依次对其进行 getBean 操作，然后使用 advisorAdapterRegistry.wrap() 将其包装成 Advisor。</p>
<p>来到 advisorAdapterRegistry.wrap()：</p>
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<pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">DefaultAdvisorAdapterRegistry</span> <span class="kd">implements</span> <span class="n">AdvisorAdapterRegistry</span><span class="o">,</span> <span class="n">Serializable</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">    <span class="kd">public</span> <span class="n">Advisor</span> <span class="nf">wrap</span><span class="o">(</span><span class="n">Object</span> <span class="n">adviceObject</span><span class="o">)</span> <span class="kd">throws</span> <span class="n">UnknownAdviceTypeException</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">		<span class="c1">//如果要封装的对象本身就是Advisor类型的，无须做任何处理
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>		<span class="k">if</span> <span class="o">(</span><span class="n">adviceObject</span> <span class="k">instanceof</span> <span class="n">Advisor</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">			<span class="k">return</span> <span class="o">(</span><span class="n">Advisor</span><span class="o">)</span> <span class="n">adviceObject</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">		<span class="o">}</span>
</span></span><span class="line"><span class="cl">		<span class="c1">//因为此封装只对Advisor和Advice两种类型的数据有效，如果不是将不能封装
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>		<span class="k">if</span> <span class="o">(!(</span><span class="n">adviceObject</span> <span class="k">instanceof</span> <span class="n">Advice</span><span class="o">))</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">			<span class="k">throw</span> <span class="k">new</span> <span class="n">UnknownAdviceTypeException</span><span class="o">(</span><span class="n">adviceObject</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">		<span class="o">}</span>
</span></span><span class="line"><span class="cl">		<span class="n">Advice</span> <span class="n">advice</span> <span class="o">=</span> <span class="o">(</span><span class="n">Advice</span><span class="o">)</span> <span class="n">adviceObject</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">		<span class="k">if</span> <span class="o">(</span><span class="n">advice</span> <span class="k">instanceof</span> <span class="n">MethodInterceptor</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">			<span class="c1">//如果是MethodInterceptor类型则使用DefaultPointcutrAdvisor封装
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>			<span class="c1">// So well-known it doesn&#39;t even need an adapter.
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>			<span class="k">return</span> <span class="k">new</span> <span class="n">DefaultPointcutAdvisor</span><span class="o">(</span><span class="n">advice</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">		<span class="o">}</span>
</span></span><span class="line"><span class="cl">		<span class="c1">// 如果存在Advisor类型的适配器那么也同样需要进行封装
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>		<span class="k">for</span> <span class="o">(</span><span class="n">AdvisorAdapter</span> <span class="n">adapter</span> <span class="o">:</span> <span class="k">this</span><span class="o">.</span><span class="na">adapters</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">			<span class="c1">// Check that it is supported.
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>			<span class="c1">// @Before,@After使用的DefaultPointcutAdvisor
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>			<span class="k">if</span> <span class="o">(</span><span class="n">adapter</span><span class="o">.</span><span class="na">supportsAdvice</span><span class="o">(</span><span class="n">advice</span><span class="o">))</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">				<span class="k">return</span> <span class="k">new</span> <span class="n">DefaultPointcutAdvisor</span><span class="o">(</span><span class="n">advice</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">			<span class="o">}</span>
</span></span><span class="line"><span class="cl">		<span class="o">}</span>
</span></span><span class="line"><span class="cl">		<span class="k">throw</span> <span class="k">new</span> <span class="n">UnknownAdviceTypeException</span><span class="o">(</span><span class="n">advice</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">	<span class="o">}</span>
</span></span><span class="line"><span class="cl"><span class="o">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>上面源码逻辑比较简单：</p>
<ol>
<li>首先判断传入的实例是否为 Advisor 实现类，如果为 true 不作任何处理，直接返回。</li>
<li>对 MethodInterceptor 的实例，包装成 DefaultPointcutAdvisor 返回。</li>
<li>循环成员 adapters 中预定义的所有 AdvisorAdapter，进行适配操作，如果有适配器支持这个 Advice，就包装成 DefaultPointcutAdvisor 返回。</li>
<li>如果以上条件都未处理成功，直接抛出异常。所以这里传入的对象一定得是一个 Advice 实现。</li>
</ol>
<p>其实我们自定义的切面类中的通知增强，在这里都已经包装为 Advisor了，大多数都是走的直接返回。
<span id="adapters-init"></span></p>
<p>关于成员变量 adapters，是在无参构造中初始化的:</p>
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<pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">DefaultAdvisorAdapterRegistry</span> <span class="kd">implements</span> <span class="n">AdvisorAdapterRegistry</span><span class="o">,</span> <span class="n">Serializable</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">    <span class="kd">public</span> <span class="nf">DefaultAdvisorAdapterRegistry</span><span class="o">()</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">		<span class="c1">// 注册三种适配器。
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>		<span class="n">registerAdvisorAdapter</span><span class="o">(</span><span class="k">new</span> <span class="n">MethodBeforeAdviceAdapter</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">		<span class="n">registerAdvisorAdapter</span><span class="o">(</span><span class="k">new</span> <span class="n">AfterReturningAdviceAdapter</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">		<span class="n">registerAdvisorAdapter</span><span class="o">(</span><span class="k">new</span> <span class="n">ThrowsAdviceAdapter</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">	<span class="o">}</span>
</span></span><span class="line"><span class="cl"><span class="o">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>关于 MethodInterceptor、 Advice、 AdvisorAdapter暂且跳过。</p>
<h2 id="3-生成代理实例---getproxy">3 生成代理实例 - getProxy</h2>
<p>getProxy() 中只有一行代码：</p>
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<pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">ProxyFactory</span> <span class="kd">extends</span> <span class="n">ProxyCreatorSupport</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">	<span class="kd">public</span> <span class="n">Object</span> <span class="nf">getProxy</span><span class="o">(</span><span class="nd">@Nullable</span> <span class="n">ClassLoader</span> <span class="n">classLoader</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">		<span class="c1">//根据目标对象是否有接口来判断采用什么代理方式，cglib代理还是jdk动态代理
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>		<span class="k">return</span> <span class="n">createAopProxy</span><span class="o">().</span><span class="na">getProxy</span><span class="o">(</span><span class="n">classLoader</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">	<span class="o">}</span>
</span></span><span class="line"><span class="cl"><span class="o">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><hr>
<p>先看第一个方法 createAopProxy()。
步骤一（注意调用下一步方法的参数）：</p>
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<pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">ProxyCreatorSupport</span> <span class="kd">extends</span> <span class="n">AdvisedSupport</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="kd">protected</span> <span class="kd">final</span> <span class="kd">synchronized</span> <span class="n">AopProxy</span> <span class="nf">createAopProxy</span><span class="o">()</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">		<span class="k">if</span> <span class="o">(!</span><span class="k">this</span><span class="o">.</span><span class="na">active</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">			<span class="n">activate</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">		<span class="o">}</span>
</span></span><span class="line"><span class="cl">		<span class="k">return</span> <span class="n">getAopProxyFactory</span><span class="o">().</span><span class="na">createAopProxy</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">	<span class="o">}</span>
</span></span><span class="line"><span class="cl"><span class="o">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>从上面代码看出，会调到另一个方法，注意这个参数，传入了一个 AdvisedSupport，里面封装了通知方法、切点等信息。
步骤二：</p>
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<pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">DefaultAopProxyFactory</span> <span class="kd">implements</span> <span class="n">AopProxyFactory</span><span class="o">,</span> <span class="n">Serializable</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">	<span class="nd">@Override</span>
</span></span><span class="line"><span class="cl">	<span class="kd">public</span> <span class="n">AopProxy</span> <span class="nf">createAopProxy</span><span class="o">(</span><span class="n">AdvisedSupport</span> <span class="n">config</span><span class="o">)</span> <span class="kd">throws</span> <span class="n">AopConfigException</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">		<span class="k">if</span> <span class="o">(</span><span class="n">config</span><span class="o">.</span><span class="na">isOptimize</span><span class="o">()</span> <span class="o">||</span> <span class="n">config</span><span class="o">.</span><span class="na">isProxyTargetClass</span><span class="o">()</span> <span class="o">||</span> <span class="n">hasNoUserSuppliedProxyInterfaces</span><span class="o">(</span><span class="n">config</span><span class="o">))</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">			<span class="n">Class</span><span class="o">&lt;?&gt;</span> <span class="n">targetClass</span> <span class="o">=</span> <span class="n">config</span><span class="o">.</span><span class="na">getTargetClass</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">			<span class="c1">// 如果目标类是一个接口，则使用JDK动态代理
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>			<span class="k">if</span> <span class="o">(</span><span class="n">targetClass</span><span class="o">.</span><span class="na">isInterface</span><span class="o">()</span> <span class="o">||</span> <span class="n">Proxy</span><span class="o">.</span><span class="na">isProxyClass</span><span class="o">(</span><span class="n">targetClass</span><span class="o">))</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">				<span class="k">return</span> <span class="k">new</span> <span class="n">JdkDynamicAopProxy</span><span class="o">(</span><span class="n">config</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">			<span class="o">}</span>
</span></span><span class="line"><span class="cl">			<span class="c1">// 使用cglib代理。
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>			<span class="k">return</span> <span class="k">new</span> <span class="n">ObjenesisCglibAopProxy</span><span class="o">(</span><span class="n">config</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">		<span class="o">}</span>
</span></span><span class="line"><span class="cl">		<span class="k">else</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">			<span class="k">return</span> <span class="k">new</span> <span class="n">JdkDynamicAopProxy</span><span class="o">(</span><span class="n">config</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">		<span class="o">}</span>
</span></span><span class="line"><span class="cl">	<span class="o">}</span>
</span></span><span class="line"><span class="cl"><span class="o">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>从上面代码可以看出，将 AdvisedSupport 封装到了创建代理的对象中。</p>
<p>有两种情况，可能会使用 JDK 动态代理、或者使用 Cglib 子类代理。无论是xml方式还是注解方式配置，激活代理时都可以配置一个布尔类型的属性 proxyTargetClass，如果不配置，默认值是 false。这个属性的作用是：指明是否要创建基于子类（CGLIB）的代理，而不是基于Java标准接口的代理。</p>
<p>默认是使用 JDK 动态代理，如果配置了 proxyTargetClass=true，会默认使用 Cglib 子类代理，但如果被代理的类本身是接口的话，依然会使用JDK动态代理。</p>
<p>以上规律从上面的源码中可以看到，在两个 if 条件中判断的。</p>
<hr>
<p>接着看 getProxy()，这里真正生成了代理对象，以 JDK 动态代理为例（cglib也类似，其实都是将 Advisor 的必要信息封装到一个类中，将执行行为封装到对应的回调函数中）：</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt">1
</span><span class="lnt">2
</span><span class="lnt">3
</span><span class="lnt">4
</span><span class="lnt">5
</span><span class="lnt">6
</span><span class="lnt">7
</span><span class="lnt">8
</span><span class="lnt">9
</span></code></pre></td>
<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">final</span> <span class="kd">class</span> <span class="nc">JdkDynamicAopProxy</span> <span class="kd">implements</span> <span class="n">AopProxy</span><span class="o">,</span> <span class="n">InvocationHandler</span><span class="o">,</span> <span class="n">Serializable</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">	<span class="kd">public</span> <span class="n">Object</span> <span class="nf">getProxy</span><span class="o">(</span><span class="nd">@Nullable</span> <span class="n">ClassLoader</span> <span class="n">classLoader</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">		<span class="n">Class</span><span class="o">&lt;?&gt;[]</span> <span class="n">proxiedInterfaces</span> <span class="o">=</span> <span class="n">AopProxyUtils</span><span class="o">.</span><span class="na">completeProxiedInterfaces</span><span class="o">(</span><span class="k">this</span><span class="o">.</span><span class="na">advised</span><span class="o">,</span> <span class="kc">true</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">		<span class="n">findDefinedEqualsAndHashCodeMethods</span><span class="o">(</span><span class="n">proxiedInterfaces</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">		<span class="c1">// 创建代理对象，参数中的InvocationHandler传入的是this，那么本类中一定有invoke()，在调用代理类方法时，就会执行这个invoke()。
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>		<span class="k">return</span> <span class="n">Proxy</span><span class="o">.</span><span class="na">newProxyInstance</span><span class="o">(</span><span class="n">classLoader</span><span class="o">,</span> <span class="n">proxiedInterfaces</span><span class="o">,</span> <span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">	<span class="o">}</span>
</span></span><span class="line"><span class="cl"><span class="o">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>源码中调用了 Proxy.newProxyInstance() 生成代理，这是典型的 JDK 动态代理的生成方式。
<div class="details admonition note open">
        <div class="details-summary admonition-title">
            <i class="icon fas fa-pencil-alt fa-fw"></i>注意<i class="details-icon fas fa-angle-right fa-fw"></i>
        </div>
        <div class="details-content">
            <div class="admonition-content"><p>仔细看 <code>Proxy.newProxyInstance(classLoader, proxiedInterfaces, this)</code>，这里第三个传输是 this，那么这个 this 一定实现了 InvocationHandler 接口、并实现了 invoke()。</p>
<p>记一下 <code>JdkDynamicAopProxy</code> 的声明： <code>final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializable</code></p>
<p>可以看到 JdkDynamicAopProxy 实现了 InvocationHandler。</p>
</div>
        </div>
    </div></p>
<p>到这里，代理对象创建完成。</p>
<p>动态代理的入口方法 wrapIfNecessary() 到这里执行完成，会将创建的代理对象返回。将代码执行流程回转到 doCreateBean 中:</p>
<blockquote>
<p>&ndash;&gt; wrapIfNecessary()<br>
&ndash;&gt; postProcessAfterInitialization()<br>
&ndash;&gt; applyBeanPostProcessorsAfterInitialization()<br>
&ndash;&gt; applyBeanPostProcessorsAfterInitialization()<br>
&ndash;&gt; initializeBean()<br>
&ndash;&gt; exposedObject = initializeBean(beanName, exposedObject, mbd);</p>
</blockquote>
<p>实际上，Spring对AOP的支持，这一整块儿，都是基于 BeanPostProcessor.applyBeanPostProcessorsAfterInitialization() 完成的。</p>
<p>冗长的流程，最终回转到 doCreateBean 中，在遍历 BeanPostProcessor 并依次调用 applyBeanPostProcessorsAfterInitialization() 时，传入创建好的bean实例，返回一个实例，而AbstractAutoProxyCreator中定义了骨架方法wrapIfNecessary()，这里面返回了一个代理实例，由此沿着调用链向上返回，最终getBean()得到的就可能是一个代理实例。</p>
<p>之所以说是可能，因为后面的流程，还有一个 getObjectForBeanInstance() 执行，如果 bean 是 FactoryBean 类型，会返回 getObject() 中返回的实例。文章 <a href="/posts/spring/07-factory-bean" rel="">复杂对象的构建方式 - FactoryBean</a> 中有详细说明。</p></div>

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